﻿using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace ajayumi.develop.CSharp.Core.Web
{
    public static class FileHelper
    {
        public static Encoding GetEncoding(FileStream stream)
        {
            return GetEncoding(stream, Encoding.Default);
        }

        public static Encoding GetEncoding(FileStream stream, Encoding defaultEncoding)
        {
            Encoding targetEncoding = defaultEncoding;

            if (stream != null && stream.Length >= 2)
            {
                //保存文件流的前4个字节
                byte byte1 = 0;
                byte byte2 = 0;
                byte byte3 = 0;
                byte byte4 = 0;

                //保存当前Seek位置
                long origPos = stream.Seek(0, SeekOrigin.Begin);
                stream.Seek(0, SeekOrigin.Begin);

                int nByte = stream.ReadByte();
                byte1 = Convert.ToByte(nByte);
                byte2 = Convert.ToByte(stream.ReadByte());

                if (stream.Length >= 3)
                {
                    byte3 = Convert.ToByte(stream.ReadByte());
                }

                if (stream.Length >= 4)
                {

                    byte4 = Convert.ToByte(stream.ReadByte());

                }

                if (byte1 == 0xFE && byte2 == 0xFF)//UnicodeBe
                {
                    targetEncoding = Encoding.BigEndianUnicode;
                }
                if (byte1 == 0xFF && byte2 == 0xFE && byte3 != 0xFF)//Unicode
                {
                    targetEncoding = Encoding.Unicode;
                }
                if (byte1 == 0xEF && byte2 == 0xBB && byte3 == 0xBF)//UTF8
                {
                    targetEncoding = Encoding.UTF8;
                }
                stream.Seek(origPos, SeekOrigin.Begin);
            }
            return targetEncoding;

        }


        public static string GetFileContent(string path)
        {
            if (!File.Exists(path))
                return null;

            string content;

            using (FileStream stream = File.Open(path, FileMode.Open))
            {
                Encoding encoding = GetEncoding(stream, Encoding.Default);
                using (StreamReader sr = new StreamReader(stream, encoding))
                {
                    content = sr.ReadToEnd();
                    sr.Close();
                }
            }
            return content;
        }


    }
}
